ARLINGTON -- Little by little, the Dallas Cowboys vision of what to expect from their retooled offensive line has come into focus throughout training camp. The operative word is "little," because the projected starters have yet to line up shoulder-to-shoulder in a preseason game.

That is not expected to change Saturday in Cowboys Stadium against the St. Louis Rams (7 p.m., KTVT/Ch. 11), with center Phil Costa projected to miss his third consecutive game with a back ailment. But left guard Nate Livings, who has yet to take a preseason snap, plans to make his debut in a Dallas uniform after returning to practice this week from a hamstring injury.

That will give the Cowboys four projected starters in the trenches, plus reserve center David Arkin, to protect quarterback Tony Romo for the brunt of the team's most extended dress rehearsal in preparation for a Sept. 5 regular-season opener at the New York Giants.

How is Romo's comfort level with the guys protecting him?

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"It's comfortable," Romo said. "They're fighting. They're getting better and better, and they just keep working hard. We're going to be all right."

Livings (6-foot-4, 320 pounds), a starter for Cincinnati the past two seasons, joined right guard Mackenzy Bernadeau as the team's free-agent additions to shore up a suspect area from last season. For the first time, the two will play in tandem Saturday against the Rams.

Cowboys coach Jason Garrett said continuity among his three interior linemen "might be as important as at any position on your team" and that he is eager to gauge how the pieces are fitting together as the regular season approaches.

"They work together in combination blocks, identifying fronts ... all of that stuff that centers and [guards] need to do," Garrett said. "It is really, really important to the success of the play, the success of your run game and your pass protection. The more experience you have spending time with these guys, taking snaps together, the better you're going to be."

Livings cannot wait to turn it loose after being given a clean bill of health from Cowboys trainers.

"It's all good, baby," Livings said of his physical condition. "In the game the other day [against San Diego], when we were coming out of the tunnel, I was getting chills myself. But I wasn't playing. And that's a feeling I don't like. I'm here to play football. I'm looking forward to [Saturday]. I'm just getting my feet back under me and getting better one day at a time."

Bernadeau, who missed most of the off-season while recuperating from hip and knee surgeries, believes Livings -- a former LSU player who started 41 of his last 46 games with the Bengals -- can be a stabilizing force.

"It's good to have 'Big Nate' back," Bernadeau said. "He's a big force inside, a big influence. We're excited to have him back and give him as many reps as we can."

Livings, Bernadeau and Arkin joined starting tackles Doug Free and Tyron Smith for the majority of the first-team reps in Thursday's Silver & Blue Debut at Cowboys Stadium. Garrett said he is eager to get his projected starters together for as much work as possible in the preseason and expressed disappointment that injuries to Costa, Livings and Bernadeau during various stages of training camp prevented that.

But he'll at least see four of the five -- including both newcomers at guard -- operate together Saturday.

"You control what you can control in life," Garrett said. "We just had a rash of injuries ... Ideally, you want that starting offensive line to be in place year after year. That's not necessarily the nature of the NFL. We have some new guys. They have been banged up, and we're going to try our best to get that continuity as well as we can, as fast as we can."

In terms of the Rams' game, Livings will be under the microscope. The Cowboys' offensive line struggled to protect Romo or create running lanes in its preseason opener, a 3-0 victory over Oakland, but fared much better in Saturday's 28-20 loss to the Chargers.

Garrett envisions Livings' return as another step toward stability in the trenches.

"He's a pro. You can see that, the way he approaches it," Garrett said. "He needs to play in our offense more, [understand] the communication next to guys, the adjustments he needs to make. He's got ... a quiet intensity that we like."

Although he has yet to take the field in a Cowboys jersey, Livings went through the entire off-season with the team and pointed to training camp as a bonding experience for him and his line mates. He said the group is becoming cohesive despite minimal game snaps together in the preseason, and he is eager to showcase that.

"We're around each other all day long in meetings and talking," Livings said. "We're dealing with certain situations on the field [in practice]. That's our job: to get better every day. To get closer every day. We know what it takes. We've just got to get ready to roll."